1. Field of the Invention
The present invention generally relates to an information recording medium for recording multimedia information as optical readable code data thereon and an information recording/reproducing system using the same and, more particularly, to an information recording medium such as a paper sheet on which so-called multimedia information including audio information such as a voice, music, or the like, image information obtained from a camera, video equipment, or the like, and/or text data obtained from a personal computer, a wordprocessor, or the like, is recorded as an optical readable code pattern, an information reproducing system for optically reading the code pattern from such information recording medium and reproducing original multimedia information, and an information recording system for recording the code pattern on the information recording medium.
2. Description of the Related Art
As conventional information recording media for recording audio information such as a voice, music, and the like, various kinds of media such as a magnetic tape, an optical disk, and the like are known.
However, these information recording media have relatively high prices even when their copies are mass-produced, and generally require a large area for storage.
Furthermore, for example, the need for forwarding an information recording medium that records voice data to another person at a remote place requires much labor and time even when the medium is forwarded via mail or is directly carried.
The same problems apply to all kinds of so-called multimedia information including video information obtained from a camera, video equipment, and the like, and digital code data obtained from a personal computer, wordprocessor, and the like in addition to audio information.
In view of these problems, U.S. Ser. No. 08/407,018 (EP0670555A1) assigned to the assignee of the present application discloses a system for recording multimedia information including at least one of audio information, video information, and text data on an information recording medium such as a paper sheet in the form of a two-dimensional code pattern, defined by two-dimensionally arranging a plurality of dots, as image information which allows facsimile transmission and can be copied in a large quantity with low cost, i.e., code information, and a system for reproducing the code information recorded on the medium.
FIG. 12 shows the format of a dot code as a two-dimensional code pattern disclosed in U.S. Ser. No. 08/407,018 (EP0670555A1).
More specifically, in a dot code 10, one block 12 consists of a marker 14, a block address 16, error detection/correction data 18 for an address, and a data area 20 that stores actual data.
A large number of blocks 12 are arranged two-dimensionally (in the vertical and horizontal directions), and the dot code 10 is formed by a group of blocks 12.
Note that the marker 14 is a large black dot having a diameter of seven dots (seven data dots).
FIG. 13A shows the schematic arrangement of an information reproducing system which is disclosed in U.S. Ser. No. 08/407,018, and reproduces and outputs original multimedia information by reading the above-mentioned dot code 10.
More specifically, in this information reproducing system, a light source 22 illuminates the dot code 10 recorded on a sheet 24 serving as a recording medium, and light reflected by the dot code 10 is detected as an image signal by an image pickup unit 28 comprising, e.g., a charge-coupled device (CCD), a charge-modulated device (CMD), or the like for converting optical information into an electrical signal, via an imaging optical system 26 such as a lens. The detected image signal is amplified by a pre-amplifier 30, and the amplified signal is output.
Note that the light source 22, the imaging optical system 26, the image pickup unit 28, and the pre-amplifier 30 are arranged in an external light shielding unit 32, so as to prevent disturbance caused by external light.
The image signal amplified by the pre-amplifier 30 is binarized by a binarization circuit 34, and the binary image data is stored in an image memory 36.
Note that the image pickup unit 28 is controlled by an image pickup unit control unit 38.
For example, when the image pickup unit 28 comprises an interline transfer type CCD, the image pickup unit control unit 38 outputs, as control signals of the image pickup unit 28, a V blank signal for vertical synchronization, an image pickup element reset pulse signal for resetting an information charge, a charge transfer gate pulse signal for transferring charges accumulated on two-dimensionally arranged charge transfer/storage units to a plurality of vertical shift registers, a horizontal charge transfer CLK signal serving as a transfer clock signal for a horizontal shift register for transferring a charge in the horizontal direction and outputting it to an external device, and a vertical charge transfer pulse signal for transferring, in the vertical direction, charges of the plurality of vertical shift registers to the horizontal shift register, and the like.
The image pickup unit control unit 38 supplies, to the light source 22, a light-emitting cell control pulse used for defining the light-emission timing of the light source 22 in synchronism with the control timing of the image pickup unit 28.
The image data stored in the image memory 36 is temporarily read out, and the read-out data is supplied to a marker detection unit 40 including marker extraction.
The marker detection unit 40 detects markers 14 in units of blocks 12 of the dot code 10.
The marker extraction and detection of the marker detection unit 40 can be attained by erosion processing described in U.S. Ser. No. 08/571,776 (EP0717398A1) assigned to the assignee of the present application.
A data arrangement direction detection unit 42 detects the data arrangement direction, i.e., the skew, rotation, and direction of the dot code 10 recorded on the sheet 24 as a recording medium using the markers 14 extracted and detected by the marker detection unit 40.
A block address detection unit 44 detects block addresses on the basis of the data arrangement direction of the dot code 10 detected by the data arrangement direction detection unit 42, and also detects the true centers of the markers 14.
An address control unit 46 generates read addresses for the image memory 36 in accordance with the block addresses detected by the block address detection unit 44 and data dot reading points in the data areas 20 of the respective blocks 12 based on the true centers of the markers 14.
Therefore, the image data read out from the image memory 36 in accordance with the read addresses generated by the address control unit 46 represents a data dot pattern.
Since the dot code 10 read out from the image memory 36 is modulated (e.g., by 8-10 modulation) upon recording, the dot code 10 is subjected to 10-8 demodulation in a demodulation unit 48, and the demodulated data is input to a data memory unit 50.
Thereafter, the data read out from the data memory unit 50 is subjected to de-interleave processing in a de-interleave unit 52, and the processed data is then subjected to error correction in units of bytes in a data error correction unit 54.
The corrected data is subjected to expansion processing corresponding to compression processing executed upon recording, and the expanded data is then reproduced and output.
More specifically, when the data is multi-valued image information such as a natural image, for example, expansion processing corresponding to JPEG is performed, or when the data is binary image information such as handwritten characters, a graph, or the like, expansion processing corresponding to MR, MH, MMR, or the like is performed. On the other hand, as for characters and line images, the data is subjected to processing such as Huffman or Ziv-Lempel processing. Thereafter, the processed data is converted into display data. After the display data is converted into an analog signal, the signal is displayed on a display device such as a CRT (television monitor), an FMD (face-mounted display), or the like.
Note that the FMD is a spectacle-type monitor (handy monitor) to be worn on a user's face, and is effective for, e.g., virtual reality applications, and when an image requiring a large screen is observed in a limited place.
Audio information is subjected to expansion processing corresponding to, e.g., ADPCM, and after the processed data is converted into an analog signal, the analog audio signal is output to an audio output device such as a loudspeaker, a headphone, or the like.
Of course, the character or line image data may be directly output to a page printer, plotter, or the like. That is, the character data may be printed on a paper sheet as characters by, e.g., a wordprocessor, or the line image data can be output by a plotter as a drawing or the like.
FIG. 13B shows the schematic arrangement of an information recording system which is disclosed in U.S. Ser. No. 08/407,018 (EP0670555A1), and records the dot code 10.
More specifically, in this information recording system, a multimedia information input unit 58 (such as a microphone, an audio equipment, a camera, a video equipment, a personal computer, a wordprocessor, or the like) inputs digital multimedia information such as audio information, image information, text data, or the like, and the input multimedia information is supplied to a compression processing unit 60.
The compression processing unit 60 performs appropriate compression processing for the supplied multimedia information, and synthesizes compressed data as needed.
For example, the compression processing unit 60 performs ADPCM processing for audio information; compression such as Huffman, arithmetic, Ziv-Lempel, or the like for text data; general binary compression processing such as MR, MH, MMR, or the like represented by JBIG for binary image information; or still image compression processing such as DPCM, JPEG, or the like for multi-valued image information.
An error correction code is added to the compressed data by an error correction code addition unit 62, and the data is input to a data memory unit 64.
The data memory unit 64 stores the data, and thereafter, an interleave processing unit 66 performs interleave processing.
In the interleave processing, continuous data strings are appropriately distributed to separate positions so as to eliminate errors as much as possible, e.g., to improve correction performance by eliminating block errors caused by noise or the like as much as possible, when the data is recorded as an actual dot code and is reproduced.
That is, in this processing, the danger of making error correction impossible is reduced by confining generation of burst errors to generation of an error for one correction unit.
The interleaved data is subjected to, e.g., 8-10 modulation in a modulation circuit 68, and the modulated data is converted into image data, in which data "1" is represented by a black dot and data "1" is represented by a white dot, in a block dot image conversion unit 70.
At this time, a data addition unit 72 adds markers, block addresses, address error discrimination codes (CRC or the like) to the image data.
Note that the markers form a data string falling outside the range of 256 different data strings that are obtained by modulation using the modulation circuit 68. Since the markers are added after modulation, the markers can be prevented from being modulated, i.e., being hardly recognized as markers.
The image data added with data is supplied to a synthesis processing unit 74, and is synthesized with print information (an image, title, characters, and the like to be recorded on a medium) other than the generated data from a print information input unit 76. The synthesized data is converted into an output format to a printer or a data format corresponding to print plate making, and the converted data is supplied to a printer system/print plate making system 78.
The printer system/print plate making system 78 finally prints the data on a recording medium such as a sheet, a tape, a printed matter, or the like.
As disclosed in U.S. Ser. No. 08/571,776 (EP0717398A1) assigned to the assignee of the present application, a format that can improve the recording density of the above-mentioned dot code has been developed.
In this format, as shown in FIG. 14, predetermined matching pattern dots 80 are arranged at predetermined positions with respect to each marker 14, e.g., between adjacent markers in a first direction, and address dots 82 indicating block addresses are arranged at predetermined positions with respect to each marker 14, e.g., between adjacent markers in a second direction.
The pattern dot 80 and the address dot 82 are constituted by dots each having the same size as a data dot arranged in a data area 20.
In such dot code 10, since the arrangement direction and the true centers of the markers 14 serving as reading reference points of the data dots 84 can be detected using the pattern dots 80 having a predetermined pattern, the reading reference points can be easily and accurately detected.
Therefore, according to the format disclosed in U.S. Ser. No. 08/571,776 (EP0717398A1), even when a code pattern is recorded at a high density, the positions of data dots 84 can be calculated with high accuracy, and original multimedia information can be reliably reproduced.
In the dot code with the format shown in FIG. 14, each marker 14 is a large black dot having a diameter of 7 dots, as described above, and a blank portion (white area) is assured around the marker 14, as shown in FIG. 15. Therefore,.each marker 14 requires a size of 11 dots.times.11 dots including the white area.
On the other hand, the pattern dots 80 are arranged in an area of 1 dot.times.30 dots to have a predetermined pattern, and the address dots 82 are arranged in an area of 22 dots.times.1 dot.
In the horizontal direction, five dots are required from the position of the pattern dots 80 to the edge of the white area of the marker 14, 22 dots are required from the edge of the white area of the marker to that of the next marker, and another five dots are required from the edge of the white area of the next marker to the position of the pattern dots of a neighboring block. Therefore, the total number of dots in the horizontal direction of one block is 33.
In the vertical direction, five dots are required from the position of the address dots 82 to the edge of the white area of the marker, 30 dots are required from the edge of the white area of the marker to that of the next lower marker, and another five dots are required from the edge of the white area to the position of the address dots of the next lower block. Therefore, the total number of dots in the vertical direction of one block is 41.
Therefore, the total number of dots per block, i.e., the area occupied by one block, is 33 dots.times.41 dots=1,353 dots.
However, of the 1,353 dots, the actual data area 20 corresponds to a portion from which the markers 14, the pattern dots 80, and the address dots 82 are excluded. For this reason, the data area 20 has only a size of 1,180 dots excluding 121 dots+30 dots+22 dots.
Since data to be recorded on this data area 20 is subjected to 8-10 modulation as described above, the number of actually effective dots is 944.
Therefore, 409 dots=1,353 dots (the total number of dots per block)-944 dots (the number of effective dots) are redundant dots, resulting in a redundancy of 30% (=409/1,353).